Lubricants



2,804,430 1C6 Patented'A g- 1957 LUBRICANTS Albert G. Rocchini, Springdale, Pa., assignor to Gulf Research 8; Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application October 29, 1953, Serial No. 380,174

2 Claims. (Cl. 252-336) This invention relates to the lubrication of metal sur faces and more particularly to lubricating surfaces of metals such as aluminum, magnesium, Monel metal and the like during rolling or other severe cold working.

When metals are cold Worked by rolling, drawing, upsetting or similar process, the metal is subjected to severe stresses which are ordinarily relieved by an annealing operation subsequent to the cold working. In order to obtain a finished product having a smooth, unmarred surface, it is necessary to lubricate the surface of the metal during the cold working operation. It is desirable to use a lubricant which in addition to having the necessary lubricating properties will be removed from the metal during the annealing Without staining or forming a dark colored residue on the surface of the metal in order to avoid the expense of a separate cleaning operation for removing the lubricant from the metal between the cold working and annealing operations.

The use of distillate mineral oils of relatively high volatility alone as a lubricant for the rolling of light colored metals like aluminum and magnesium does not solve the problem. While those oils may be substantially completely removed during the annealing, they do leave an objectionable stain or even a gummy residue on the surface of the metal after annealing unless the oil is washed or otherwise removed from the metal prior to annealing. Moreover, light oils are relatively inflammable and the high temperatures developed and splinters of magnesium formed during the rolling of magnesium cause a serious fire hazard which makes the use of light mineral oils as lubricants for this purpose unsatisfactory.

Emulsions or solutions of soluble" mineral oils in relatively large amounts of Water eliminate the fire hazard mentioned above, but tend to etch and stain the surface of the metals. Water alone cannot be used satisfactorily because it does not have adequate lubricating properties to prevent damage to the surface of the metal.

This invention resides in the lubrication of the surfaces of metal such as aluminum, stainless steel, Monel metal and particularly magnesium during severe cold working such as rolling or drawing with a dispersion of a watersoluble silicone material and a lubricating oil in water. The term dispersion is used to designate either an emulsion fo the several constituents of the composition or a solution of the silicone material and soluble mineral oil in water. The dispersion is prepared by thorough mixing of the several constituents to form the composition.

The term water-soluble silicone material is used in this specification to designate water-soluble salts of an alkyl siliconic acid. A preferred Water-soluble silicone material is a Water solution of sodium methyl siliconate which may be either in the monomeric or polymeric form. The preparation of water soluble alkali metal siliconates is described in Patent No. 2,507,200 of Elliott et al., issued May 9, 1950. A water-soluble silicone material which may be employed is a water solution of sodium methyl siliconate marketed by the General Electric Company under the trade name SC-50. This material has total solids content of 3l.2- -2.8% of which 20.0i0.5% are silicone solids. The material has a specific gravity of 1.23 to 1.25, a viscosity at 100 F. of 5-7 centistokes and a pour point below 5 F.

The lubricating oil employed in the compounding of the lubricants of this invention may be either synthetic oils such as light oils of the desired viscosity from Fischer- Tropsch processes, esters of dibasic acids, and oils from the polymerization of olefins, or, preferably, soluble mineral oils. The soluble mineral oils which are readily available ordinary commercial products consists, in general, of a mineral oil with an emulsifier dispersed therein which allows the formation of stable emulsions of the mineral oil in water. The mineral oils suitable for this invention are the more volatile oils which may be evaporated from the surface fo the metal during the annealing operation subsequent to the cold working of the metal, thereby eliminating the necessity of a seperate washing step. In general, the preferred mineral oils are those which are prepared as distillates and will have an SUS viscosity at 100 F. from about 50 to 300. The viscosity is primarily an indication of Whether or not the oil is sufliciently light or volatile to be removed readily from the surface of the metal since the non-staining property of the lubricant is of primary importance. The mineral oil employed in compounding the lubricants of this invention may be derived from any suitable lubricating base such as those obtained from the paraffiriic, naphthenic, or mixed base crudes. The requirements in regard to the oiliness or lubricating properties of the composition are not particularly severe for the service contemplated and are rather easily met by mineral oils commonly employed as lubricants.

A large number of emulsifiers employed in the preparation of soluble mineral oils are available as ordinary commercial products. Non-ionic emulsifiers such as polyoxyethylene sorbitan oleates are often used. Other suitable emulsifiers are the sodium petroleum sulfonates, soaps of faty acids, alkanol amine soaps of fatty acids, rosin acids, and naphthenic acids, esters of ethylene glycol and polyethylene glycols, and polyoxyethylene ethers of the higher fatty alcohols and alkylphenols. The emulsifiers may be incorporated in the mineral oil to form a soluble mineral oil for compounding the lubricants of this invention or may be added directly with the mineral oil, water and Water-soluble silicone material in preparing the final composition. The emulsifiers aid in the formation of a stable dispersion of the lubricating oil in the water.

The amount of water in the lubricant composition will depend upon the severity of the working of the metal and the lubrication required to prevent damage to the surface of the metal. Water may constitute as much as percent of the lubricant composition in operations of low severity such as a mild rolling of magnesium and as little as 50 percent of the composition in situations where the metal is severely worked and better lubricating properties are required of the lubricant.

The lubricating oil will constitute a maximum of ap proximately 60 percent of the constituents other than Water added as such in the lubricant, herein designated as non-aqueous constituents, and a minimum of approximately 20 percent of those constituents. In compositions in which the lubricating oil is a mineral oil, it is desirable to maintain the concentration of the mineral oil as high as possible in the lubricant composition consistent with obtaining a non-staining lubricant because of the lower cost of the mineral oil as compared with the silicone material and the greatly superior lubricating properties of the mineral oils in this service. At higher concentrations of water in the final lubricant composition, the soluble mineral oil will be near the upper limit of 60 percent of' the non-aqueous constituents, particularly when the emulsifier in the soluble oil is of the non-ionic type.

The water-soluble silicone material will range from 40 percent to as much as about 80 percent of the nonaqueous constituents. Since the non-aqueous constituents constitute from about 5 to about 50 percent of the total lubricant composition, the water-soluble silicone material could range from about 2 to 40 percent of the total lubricant composition. However, as mentioned in the preceding paragraph, at higher water concentrations the soluble mineral oil concentration is near the upper limit of 60 percent of the non-aqueous constituents, hence, the concentration of the water soluble silicone material will lie in the range of about 2 /2 to 40 percent of the total composition. A preferred non-staining rolling oil for the lubrication of magnesium is a dispersion of approximately 85 to 95 percent water, 2 /2 to 7 /2 percent water-soluble silicone material and 2 /2 to 7% percent of a soluble mineral oil having an SUS viscosity of about 100 seconds at 100 F.

According to this invention the surfaces of the metal being worked are lubricated by establishing and maintaining thereon a film of the lubricant composition of this invention. It has been found that it is not necessary to remove the lubricant from the surface of the metal prior to annealing andthat upon annealing the metal subsequent to working it, the lubricant is removed to leave the metal with an acceptable, surface free of a dark colored residue. Metals lubricated in this manner may be cold worked without the formation of surface defects or the galling or sticking to the rolls which are experienced if the metal is cold worked without a lubricant.

The non-staining characteristics of the lubricant compositions of this invention are illustrated by a series of burn-off tests made on magnesium test plates. In a single plate test, 0.2 of a milliliter of a 10 percent.dispersion in water of the non-aqueous constituents being tested is spread over the entire surface (2 /29 by 2 /2) of a magnesium test plate. The plate is' then placed .on the floor of an electric muffie furnace which is held at the proper test temperature for a period of 30 minutes. Tests were run with the muffle furnace at 400 F. and also at 800 F. At the. end of the test, the plateis removed, cooled and inspected for stains. The same procedure as described above for the single platetest was employed for a double plate test with the exception that the dispersion was sandwiched between'twov magnesium test plates. The results of the burn-off tests are set forth in Table I.

TABLE I Burn-0]?" stain characteristics of dispersions of 10% non-aqueous constituents and 9% water on magnesium strips 400 F. for hr. 800 F. for hr. N oil-aqueous Constituents Single Plate Double Single Double Plate Plate Plate Brow-n Gummy Stain Poor Poor" Poor.

Poor.

Brown Gummy Resi- Poor- Poor.- Poor.

duePoor. 50%A+50% O. Good Good- Good. Good. 50% B+50% 0... Fair Fair--. Fair.-- Fair.

C-General Electric SO50.

Stains or residues that are white or gray are listed in Table I as good. A yellow, amber or very light brown stain is listed as fair. Any. stains darker than very light brown are listed as poor. Stains listed as either good. or fair give products with acceptable finishes.

The compositions of this invention can be prepared having a,,wide range of viscosities and lubricating properties and are readily and substantially completely removed from the surface of the metal during the annealing operationto leavethe surface of the metal free of colored. stains or residues. Moreover, the compositions also areefiective as a quenching medium preventing fires during the rolling of magnesium. Maintaining a film of the lubricant on the surface of the metal during cold working is effective in preventing damage to the surface of the metal.

I claim:

1.,A non-staining composition for the lubrication of aluminum, magnesium, and like metals during severe cold working consisting essentially of 2 /2 to 40% sodium methyl siliconate, 2% to 30% of a mixture of a mineral oil having a SUS viscosity at 100-F. in the. range of 50 to 300 and an emulsifier in minor amounts sufiicient to form a stable dispersion of the mineral oil in water, and 50 to 95% water.

2. A non-staining composition for the lubrication of aluminum, magnesium, and like metals during severe cold working consisting essentially of 2 /2 to 7%% sodium methyl siliconate, 2 /2 to 7 /z% of a mixture of a mineral oil having a viscosity in the range of 50 to 300 SUS at 100 F. with a minor amount of an emulsifier sufiicient to form a stable emulsion of the mineral oil in water, and to water.

References Cited in the file of this patent UNITED STATES PATENTS 2,346,157 Farrington et al. Apr. 1, 1944 

1. A NON-STAINING COMPOSITION FOR THE LUBRICATION OF ALUMINUM, MAGNESIUM, AND LIKE METALS DURING SERVES COLD WORKING CONSISTING ESSENTIALLY OF 21/2 TO 40% SODIUM METHYL SILICONATE, 21/2 TO 30% OF A MIXTURE OF A MINERAL OIL HAVING IN SUS VISCOSITY AT 100*F. IN THE RANGE OF 50 TO 300 AND AN EMULSIFER IN MINOR AMOUNTS SUFFICIENT TO FORM A STABLE DISPERSION OF THE MINERAL OIL IN WATER, AND 50 TO 95% WATER. 